Many of the websites are niche dating ones similar to Ashley Madison, according to a list compiled by Hold Security, a Wisconsin-based company that specializes in analyzing data breaches. A few are job-related sites.

Batches of stolen information were found on a server by the company’s analysts, said Alex Holden, Hold Security’s founder and CTO. The server, for some reason, was not password protected, allowing analysis of its contents, he said.

None of the dating sites are nearly as prominent as Ashley Madison, which saw sensitive company information, emails, internal documents and details of 30 million registered users released in a devastating data breach. Holden said this Russian-speaking group is not related to Impact Team, which claimed credit for the intrusion into Ashley Madison.